As an AV interface for digital home appliances, an HDMI (High-definition multimedia interface, registered trademark) is in widespread use. The HDMI is a digital interface for high-speed transmission of baseband signals containing signals of images (moving images) and sound signals accompanying the images. The HDMI standard is a standard arranged for AV (Audio Visual) devices by adding a sound transmission function and a copyright protection function to DVI (Digital Visual Interface) as a connection standard for PCs (Personal Computers) and displays.
There are three types of devices connected via HDMI of an HDMI source, an HDMI sink, and an HDMI repeater. The HDMI source is a device that outputs signals of images and sound via HDMI, and the HDMI sink is a device that receives and reproduces signals of images and sound. The HDMI repeater is a device including one or more input terminals and one or more output terminals and having a function of distribution and switching of signals, and relays between the HDMI source and the HDMI sink.
The HDMI has a content transmission channel (signal channel) for transmitting signals of images and sound of the baseband from the HDMI source via the necessary HDMI repeater to the HDMI sink. The HDMI has a control signal transmission channel (control channel) for interactively transmitting control signals (control data). The control signal transmission channel is a transmission channel for DDC (Display data channel) and CEC (Consumer Electronics Control). The DDC transmits EDID (Extended Display Identification data) describing properties of the number of pixels and the size of the display. The CEC is a function of controlling the devices connected via HDMI. These transmission channels, a 5V power supply, grounds for the respective signals are collected in one HDMI cable.
The devices connected via the HDMI cable may be remotely operated using CEC. For example, when a play button of a reproducing device connected to a broadcast receiving device by an HDMI cable is pressed, power of the broadcast receiving device is turned on and enables operation of switching the input of the broadcast receiving device to the input to which the reproducing device is connected. For realization of the input switching, addresses indicating the physical connection relation of the devices (called “physical addresses”) are used.
The broadcast receiving device (root) located at the peak of the connection tree has a physical address “0.0.0.0”. The device connected to the broadcast receiving device acquires a different physical address in response to the input terminal to which the device is connected. The physical addresses are stored in an EDID-ROM that the broadcast receiving device has inside. In the case where “2.0.0.0” is stored as a physical address in the input terminal of the broadcast receiving device, the device connected to the input terminal, for example, an AV amplifier acquires the physical address by DDC (Display Data Channel) communication, and recognizes the acquired physical address as the physical address of the device. Further, a Blu-ray Disc (BD, registered trademark) player connected to the AV amplifier reads out the EDID-ROM of the terminal to which the player is connected and acquires a physical address “2.1.0.0”.
The respective devices in connection may grasp the mutual connection relations by the physical addresses. For example, the respective sources connected to the broadcast receiving device transmit the acquired physical addresses using CEC commands. The broadcast receiving device may determine from which input terminal content data is supplied depending on the received physical address, and selects appropriate input.
Patent Document 1 (JP-A-2009-2465140) discloses solution to a problem caused by presence of a device specified with its own EDID-ROM unreadable when the power is in the standby state.